The Key to Efficient Multitasking: One Thing at a Time

Imagine Julia, a 30-ish marketing executive always on the go. She organizes meetings and conference calls, answers e-mails throughout the day, and of course Tweets in real time, reacting to the latest news. Bounding with energy, Julia prides herself on being a multitasker—except that she really isn't any more than her bogged-down computer can honestly multitask either (more on that in a moment).

Julia knows she is smart and is proud of her brainpower. As a science buff, she knows that the brain is the most complex object in the universe, and that its adaptability is why humans have survived for hundreds of thousands of years. What Julia doesn't know, on the other hand, is that the brain's adaptability has limits and that we may have reached them today.

Let's start with Julia's irksome computer first. A phrase heard often around her office is, "My system is slow." In the early days of personal computing, companies like Microsoft made a selling point of the software's ability to handle several tasks at once. The claim was literally false, however. Instead of really doing five tasks simultaneously, for example, which would be true multitasking, the processor spent one-fifth of a second on the first task (e-mail, for instance), the next fifth on the second task (browsing), the third fifth on a spreadsheet perhaps, and so on, looping over and over until everything got done. Such a start-and-stop approach is highly inefficient because it takes longer to do the work than if the operating system had handled each task sequentially one by one. This is why computers slow to a crawl or freeze up and drive us crazy in the process.

I've got it covered.

Now, what about Julia's brain? The same inefficiency that freezes up your computer bogs down a brain when it is forced to divide attention among multiple tasks.

The world has changed enormously since the dawn of humankind, yet we still have the same brain as our distant ancestors. The last two decades alone have served up an explosion of attention-grabbing technology—smartphones, iPads, social networking, messaging, YouTube—that tax the brain's attention circuits beyond the breaking point.

Any plausibly salient stimulus that might grab our attention has to pass through a single chokepoint in the brainstem, and from there branch to three way stations in the cortex so that attention can focus itself onto appropriate targets. Think of it as aiming and focusing a searchlight. In our case, we employ a sensory map to tell us what we're dealing with, a motor map for directing exploration out into the outside world, and a motivational map concerned with expectation, salience, and emotional vigilance. That is, our attentional circuits guide looking, listening, touching, and exploring.

We've all witnessed or at least heard about texting drivers who veer into oncoming traffic, or pedestrians so absorbed in their cellphone conversations that they walk into lampposts. "They're not paying attention," critics say. That's true, but more accurately they cannot pay attention to their surroundings. Their bodies may be located where their phones are, but their minds are far away, making it all too easy to crash into traffic or walk into lampposts. In a world of nonstop distraction, you may be able to juggle things for a while, but you can't keep it up; it simply takes more energy and bandwidth than we have.

People complain of time compression and the abundance of junk information that eats up enormous amounts of time. Time no longer flies; it scarcely exists. And yet the brain rewards us whenever our attention circuits are activated, making us alert and stimulated. This may make it hard to fall asleep at night, but that's the way it's designed to be. It is why smartphones and the like are so highly addictive, alternating relentless stimuli with dopamine rewards. In the face of constant hits, we can't quit. Worse, the ability of friends, family, and bosses to change their minds at the last moment has brought about the death of certainty. Constantly on-call, we live in a cult of flexibility where planning is impossible.

So what might our friend Julia do? Studies have demonstrated what ought to be common sense: that people think more deeply when they are not distracted. If Julia has come to realize that she can have either e-mail or a life, then it is time for her to unplug if only for a while.

Actually, poor computer analogy. If the task does depend in question depends on user input, which from the computer standpoint happens pretty infrequently, or network communications, which are orders of magnitude slower than internal, then it is inefficient to spent that time waiting when other tasks could be moved forward.